P03.11.A Potential role of pre-radiotherapy MRI for target delineation in high-grade gliomas: a multicenter retro-prospective cohort study

Abstract Background The optimal timing for target identification in high-grade glioma (HGG) remains unclear due to variability the hyper-signal T2/FLAIR between MRI performed at diagnosis, post-surgery and radiotherapy (RT) start. aim of this study was retrospectively confirm that RT planned on delayed might allow spare more normal tissue without decreasing local tumour control, order prospectively evaluate best standard advanced metabolic imaging sequences clinical tumor volume (CTV) adaptation. Material Methods We analyzed a retrospective cohort consecutive patients with HGG treated from 2017 2020. All had diagnostic another immediately or pre-RT. Target volumes were contoured, based T2/FLAIR, group A, while B pre-RT MRI. GTV CTV volume, percentage increase them. Moreover, we compared two groups terms clinical-pathological characteristics progression-free survival (PFS) overall (OS). A prospective study, started January 2022, has enrolled evaluated by In addition, some selected have undergone DOPA-PET DOPA-PET. 2 MRI-guided contours been each patient: adapted CTV-adapt pre-RT, assess objectives. Results 54 (25 29 B). median age 61 years (IQR 17,75), 93% an ECOG PS 0 1, 51 symptomatic diagnosis. Patients frequently MGMT methylation (59 % vs. 28%, p=0.01) less frontal lobe involvement (60% 24%, p=0.01). higher than B: 431% (range 62%-7335%) vs 385% 53%-3174%), respectively. No significant difference pattern relapse observed, since >90% disease recurrences in-field both groups. Median PFS OS population 9.5 months (95% CI 7 - 12) 18.5 16 24), better as those (p=0.03), but similar OS. Nevertheless, imbalance MTMT status major driver PFS. Overall, 37 out improvement neurological symptoms (p<0.001), no (p=0.54). Conclusion Our data suggest adaptation may reducing affecting relieving control. will help identifying guided imaging, optimize efficacy safety treatment planning.